nft: Optimize flushing all chains of a table

Leverage nftables' support for flushing all chains of a table by
omitting NFTNL_RULE_CHAIN attribute in NFT_MSG_DELRULE payload.

The only caveat is with verbose output, as that still requires to have a
list of (existing) chains to iterate over. Apart from that, implementing
this shortcut is pretty straightforward: Don't retrieve a chain list and
just call __nft_rule_flush() directly which doesn't set above attribute
if chain name pointer is NULL.

A bigger deal is keeping rule cache consistent: Instead of just clearing
rule list for each flushed chain, flush_rule_cache() is updated to
iterate over all cached chains of the given table, clearing their rule
lists if not called for a specific chain.

While being at it, sort local variable declarations in nft_rule_flush()
from longest to shortest and drop the loop-local 'chain_name' variable
(but instead use 'chain' function parameter which is not used at that
point).

Signed-off-by: Phil Sutter <phil@nwl.cc>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/iptables/nft-cache.h b/iptables/nft-cache.h
index 793a85f4..cb7a7688 100644
--- a/iptables/nft-cache.h
+++ b/iptables/nft-cache.h
@@ -8,7 +8,8 @@ void nft_build_cache(struct nft_handle *h, struct nftnl_chain *c);
 void nft_rebuild_cache(struct nft_handle *h);
 void nft_release_cache(struct nft_handle *h);
 void flush_chain_cache(struct nft_handle *h, const char *tablename);
-void flush_rule_cache(struct nftnl_chain *c);
+int flush_rule_cache(struct nft_handle *h, const char *table,
+		     struct nftnl_chain *c);
 
 struct nftnl_chain_list *
 nft_chain_list_get(struct nft_handle *h, const char *table, const char *chain);